Relationship between the kinematics of wrist/finger joint movements and muscle loading during typing in people with different skill levels

Abstract

Background Musculoskeletal disorders caused by computer use are associated with socio-economic problems. Reducing the biomechanical loading caused by hand movements could reduce the occurrence of such disorders. However, most participants recruited for past experimental studies had a certain level of typing skill, and differences in the biomechanical loading of those with different typing skills have not been examined. This study aimed to quantify the relationship between the movements of the wrist and finger joints and the loading on the forearm muscles and to clarify the differences between typists of different skill levels. Methods A 3D motion capture system measured wrist and index finger joint movements, and surface electromyography measured muscle activities for the right hand during a typing task. We compared wrist and finger joint movements and forearm muscle loading during typing, keystroke time, and key release time between skilled and unskilled typists. Findings Skilled typists move their wrists and fingers faster with less muscle activity during typing, the active tension of their finger flexor muscles during keystrokes are high, and they have higher mechanical stresses on the finger flexor tendons during keystrokes. Unskilled typists develop strategies to prevent excessive stiffness in their wrist joints when making keystrokes. They are expected to have a higher cumulative loading on the extensor muscles of the wrist during key release. Interpretation Biomechanical loading in typing skill is different, which may make it possible to predict disability. This could provide information on the changes in physical parameters and environments to prevent disability.